Telephone connector

ABSTRACT

A telephone junctor for interconnecting an electromechanical and an electronic automatic exchange, the latter using tone signaling and capable of operating in time-division-multiplex. The junctor permits direct inward dialing of a subscriber on the electromechanical exchange by a subscriber of the electronic exchange.

The present invention relates to a telephone junctor for the directinward dialing of a subscriber connected to a first automatic exchangehaving public network line equipment and extension subscriber equipment,by a further subscriber connected to a second, distant automaticexchange capable of transmitting signaling at three frequencies towardsthe said junctor and of interpreting the changes of state of the latter.

The invention relates in particular to cases wherein the second exchangecomprises an electronic automatic switching equipment, for example,operating in multiplex by time division, i.e. piloted by an electroniccomputer, and wherein the first exchange is equipped with an automaticswitching equipment of electromechanical type, not provided originallyfor such direct inward dialing.

It is impossible, with the aid of the technique known at the presentday, to interconnect the two exchanges under discussion, for achievingsuch utilization.

The junctor according to the invention permits this type of workingwithout necessity for modification of existing equipment in theexchanges concerned, the only conditions required being, in the case ofthe first exchange, to have public network line equipment and extensionsubscriber equipment, and, in the case of the second exchange, to haveavailable equipment transmitting three-frequency signaling and, since itis piloted by a computer, to be able to insert into the programming ofthe latter the sub-program necessary for long-distance control of thesaid junctor, the latter being of course disposed in the vicinity of thefirst exchange.

The telephone junctor according to the invention is characterized inthat it comprises:

A GENERATOR FOR SINGLE-FREQUENCY SIGNALING THE SIGNALS OF WHICH AREMODULATED BY "ON-OFF KEYING,"

A FIRST TERMINATING SET CONNECTED AT THE TWO-WIRE SIDE TO THE SECONDEXCHANGE AND CONNECTED AT THE FOUR-WIRE SIDE BY ITS FIRST PAIR OF WIRESON THE ONE HAND TO A CIRCUIT RECEIVING THREE-FREQUENCY SIGNALING THESIGNALS OF WHICH ARE TRANSMITTED BY THE SECOND EXCHANGE, THE SAIDRECEIVING CIRCUIT CONTROLLING RELAYS THROUGH INTERMEDIARY OF LOGICELEMENTS, AND ON THE OTHER HAND TO THE FIRST CHANNEL OF THE FOUR-WIRECIRCUIT OF A SECOND TERMINATING SET, AND CONNECTED BY ITS SECOND PAIR OFWIRES TO THE OUTPUT OF A TWO-INPUT SUMMING AMPLIFIER, THE FIRST INPUT OFWHICH IS SUBJECTED TO THE SINGLE-FREQUENCY SIGNALING; AND THE SECONDINPUT OF WHICH IS CONNECTED TO THE SECOND CHANNEL OF THE FOUR-WIRECIRCUIT OF THE SECOND TERMINATING SET, THE TWO-WIRE SIDE OF WHICH ISCONNECTED EITHER TO THE EXTENSION SUBSCRIBER EQUIPMENT OR TO THE PUBLICNETWORK LINE EQUIPMENT OF THE FIRST EXCHANGE, DEPENDING ON THE SIGNALINGTRANSMITTED BY THE SECOND EXCHANGE,

AN OFF HOOK DETECTING CIRCUIT,

A SOURCE OF A.C. SUPPLYING THE RINGING CURRENT, AND

A D.C. SOURCE SUPPLYING THE PUBLIC NETWORK LINE EQUIPMENT OF THE FIRSTEXCHANGE.

The invention will be better understood with the aid of an example ofembodiment and of the accompanying drawing showing the electric wiringdiagram of a junctor interconnecting two automatic telephone exchanges.

The said junctor is shown at 2 within a broken-line framework. The twointerconnected exchanges are, on the one hand, an automatic exchange 3comprising an automatic switching equipment of electromechanical typeconnected to the public network and an automatic exchange 4 having anelectronic automatic switching equipment operating in multiplex by timedivision. Whereas the junctor 2 is disposed in the proximity of theexchange 3, the exchange 4 may be a considerable distance from thepreceding elements. The exchange 4 is connected to the junctor 2 by atwo-wire line connected to a first terminating set 5 of known type,having a balancing network permitting passage in four-wire circuit, i.e.a first pair of wires feeding, through intermediary of an amplifier 6,on the one hand three frequency detectors 7, 8, 9 connected in paralleland corresponding respectively to frequencies f1, f2, f3 of thethree-frequency signaling system employed by the exchange 4, and on theother hand the first channel on the four-wire side of a secondterminating set T. In order to enhance the reliability of the signaling,the exchange 4 emits two of these frequencies simultaneously, i.e.either f1 + f2 or f2 + f3 or f 1 + f3, depending on the operation whichrequires to be triggered at a distance by the exchange 4 in the junctor2, as will be precisely set forth later.

The outputs of the frequency detectors 7, 8, 9 serve as inputs for asystem of three AND logic elements 10, 11, 12, having two inputs and theinputs of which are connected in pairs, each connection being effectedat the single output of one only of the detectors 7, 8, 9.

The logic element 10, the inputs of which are connected respectively tothe outputs of the detectors 7 and 8, and the logic element 11, theinputs of which are connected respectively to the outputs of thedetectors 8 and 9 have an output feeding a bistable relay R of thefour-contact type (R1, R2, R3, R4) having two positions 0 and 1. Theelement 11 feeds the winding of the relay R corresponding to theposition 0 of the said contacts, and the element 10 the winding of therelay R corresponding to position 1 of the said contacts.

The logic element 12, the inputs of which are connected respectively tothe outputs of the detectors 7 and 9 has its output connected on the onehand through intermediary of position 1 of the contact R1 to the firstinput of an AND logic element 13 having two inputs and the output ofwhich feeds a relay S having two off-on contacts S1 and S2, andconnected on the other hand through intermediary of position 0 ofcontact R1 to the winding of a relay A having a single contact.

The second pair of wires, on the four-wire side, of the firstterminating set 5 receives the output signal of a summing amplifier 14having two inputs, the first of which is connected to the mobile elementof the contact R2 through intermediary of the second channel on thefour-wire side of the second terminating set T, and the second input ofwhich is connected to a single-frequency signaling generator having afrequency f4 modulated by on-off keying in accordance with a modulationfrequency very much lower than f4, f4 itself being different from thefrequencies f1, f2, f3. In order to be entirely specific, in the examplegiven there have been adopted for f1, f2, f3, respectively, thefrequencies 700, 1300 and 1500 c/s, these frequencies forming a part ofthose which have been standardized in France by the "Societe Mixte pourle Developpement de la Commutation dans le domaine desTelecommunications SOCOTEL." There has been adopted f4 = 1100 c/s, thecorresponding sinusoidal signals being modulated by "on-off keying" insuch manner as to be present during 12 ms and then absent during 12 ms,and so on. Thus, there is utilized a generator 15 of 1100 c/s sinusoidalsignals in series with an "on-off keying" modulator 16, the output ofwhich is connected to the second input of the amplifier 14 throughintermediary of the contact R3, on its position 1, in series with abreak contact B controlled by a relay winding B, the feeding of whichwill be discussed precisely later.

The automatic exchange 3 has inter alia extension subscriber equipment,the two wires of which are connected to a winding of a transformer 17through intermediary of two series contacts, i.e. a break contact Acontrolled by the winding of the relay A and the contact R4 on itsposition 0. The second winding of the transformer 17 has one terminalconnected to earth and the other terminal connected to the contactmember 0 of the contact R2, the mobile element of which is connected tothe second terminating set T at the two-wire side. Each of the two wiresof the public network line equipment of the exchange 3 is connected toone end of the half-windings of a telephone transformer 18 throughintermediary of the break contact member of the contact S1 or S2respectively, the two half-windings being connected in series throughintermediary of a capacitor 19.

The other winding of the telephone transformer 18 has one terminalconnected to earth and the other terminal connected to the contactmember 1 of the contact R2.

The make contact elements of the contacts S1 and S2 are connected to a50 c/s feed source (of, for example, 70 V), through intermediary of afirst off hook detector 20.

The terminals of the capacitor 19 are connected to a d.c. source (forexample, 48 V) through intermediary of a second off hook detector 21.

The off hook detectors 20 and 21 separately control the winding of arelay B through intermediary of an OR logic element 22, the output ofwhich is connected to the second input of the logic element 13 throughintermediary of a logic NOT element 23.

On the off hooking taking place during the emission phase of the ringingsignal, it is the detector 20 which functions as to provoke excitationof the winding B and de-excitation of the winding S, since the secondinput of the element 13 changes state under the action of the element23. When the off hooking takes place during a silence interval of theringing signal, it is the detector 21 which intervenes, but the finalresult is the same.

The exchange 4, in application of the particular subprogram which isassociated with its intrinsic program due to the presence of the junctor2, emits at the end of each call the signal f1 + f2 for positioning thecontacts of the relay R on position 1.

The mode of functioning of the junctor 2 is as follows:

First case: A calling subscriber of exchange 4 calls the operator ofexchange 3, since he does not know the extension number of the calledsubscriber.

The exchange 4, in application of the sub-program associated with itsintrinsic programming, after having recognized that the callingsubscriber is calling the operator, then emits the signal f1 + f2, whichproduces excitation of the winding 1 of the relay R through intermediaryof the detectors 7 and 8 and the logic element 10.

The contacts R1 to R4 pass into their position 1 -- if they are notalready there -- and this connects the operator to the circuit of thecalling subscriber. In accordance with the subprogram, the exchange 4then emits, in order to ring the operator, the signal f1 + f3 during 3.3s followed by 1.6 s interruption, and so on.

The winding of relay S is then periodically excited due to the action ofthe logic elements 12, 23 and 13; the contacts S1 and S2 commence tobeat at the same rhythm, connecting the operator alternatingly to the 50c/s source (ringing) or to the d.c. source.

If the operator takes her handset off the hook, one of the off hookdetectors 20 or 21 emits a signal in the direction of the element 22,i.e. the first if this is during the emission period of the ringingsignal, the second if it is during an interval of silence of the ringingsignal.

The logic element 22 then permits, due to its output signal, excitationof the winding of relay B; the result thereof is, on the one hand,interruption of the ringer since the second input of the logic element13 rocks in the other direction, and on the other hand, opening ofcontact B, the result of which is to cause cessation of emission of the1100 c/s signal.

The exchange 4 detects the disappearance of this signal and thenestablishes relationship, by its connecting network, between the callingsubscriber and the operator of the exchange 3.

Second case: A subscriber of exchange 4 calls a subscriber of exchange3, the extension number of which he knows.

The exchange 4, recognizing a call in direct inward dialing, stores theextension number requested and then emits, in accordance with thesub-program, the signal f2 + f3. Thus, the bistable relay R switches onthe position 0 under the action of the logic element 11.

The telephone transformer 18 is cut out of circuit, as also is the 1100c/s signal, and the transformer 17 is connected to the terminating set Tby the contact R2. The contact R4 closes the loop of the extensionsubscriber equipment of the exchange 3 connected to the junctor 2. Theexchange 4 then fulfills, relative to the said extension subscriber orset, the role of a calling subscriber of exchange 3 calling anothersubscriber of the said exchange, since it remote-controls the necessaryoperations.

Thus, at the commencement the whole procedure which takes place is as ifthe extension subscriber should have its handset off the hook. Theexchange 3, recognizing such off hooking, emits the dial tone, which theexchange 4 immediately detects, subsequent to which the latter emits thedialing pulses of the called subscriber (from exchange 3), by means offrequencies f1 + f3 modulated by on-off keying in the cadence of adialing operation which would be effected with the aid of theconventional dial. Thus, the relay A commences to beat in synchronismwith this modulation. The exchange 3 then commences to emit the ringingtone which the exchange 4 detects. The latter then establishesconnection between the calling subscriber and the junctor 2, by means ofits connecting network.

Third case: A subscriber of exchange 3 calls a subscriber of exchange 4.

The calling subscriber effects the operations necessary for obtainingconnection to the public network line equipment connected to the junctor2. This connecting takes the form of closure of a loop on the publicnetwork line equipment, which the detector 21 reveals. The contact Bopens and the exchange 4 detects interruption of the 1100 c/s signal,which signifies for this exchange 4 that a subscriber of exchange 3wishes to call a subscriber of exchange 4.

The exchange 4 then transmits the dial tone. Then, the callingsubscriber dials, during which opening of the loop causes the relay B tobeat, the result of which is to interrupt, in the dialing cadence, the1100 c/s signals modulated by on-off keying. The exchange 4 detectsthese signal trains and, once the dialing of the called subscriber hasbeen analyzed by the control logic system of the exchange 4, the latterwill transmit to the calling subscriber the ringing tone, provided thatthe called subscriber has not taken his handset off the hook. Then, theremainder of the operations takes place in accordance with theconventional process.

The junctor according to the invention permits detection of the off hookof a handset even in the case of long lines, due to the three-frequencysignaling; the field of utilization thereof may be extended to theconnection of distant telephone devices, in which case no account wouldbe taken of extension subscriber equipment connections.

We claim:
 1. Telephone junctor for the direct inward dialing of asubscriber connected to a first automatic exchange having public networkline equipment and extension subscriber equipment by a furthersubscriber connected to a second, distant automatic exchange capable oftransmitting three-frequency signalling towards the said junctor and ofinterpreting the changes of state of the latter, characterised in thatit comprises:a generator of single-frequency signaling the signals ofwhich are modulated by "on-off keying," a first terminating set for twowire to four wire conversion connected at the two-wire side to thesecond exchange and connected at the four-wire side by its first pair ofwires to a circuit for receiving three-frequency signaling the signalsof which are transmitted by the second exchange, the said receivingcircuit controlling relays through intermediary of logic elements, andto the first channel of the four-wire circuit of a second terminatingset and, connected by its second pair of wires to the output of atwo-input summing amplifier the first input of which is subjected to thesingle-frequency signaling and the second input of which is connected tothe second channel of the four-wire circuit of the second terminatingset the two-wire side of which is connected either to the extensionsubscriber equipment or to the public network line equipment of thefirst exchange, in accordance with the signaling transmitted by thesecond exchange, an off hook detecting circuit, an a.c. source supplyingthe ringing current, and a d.c. source feeding the public network lineequipment of the first exchange.
 2. A junctor enabling direct inwarddialing to a first, electromechanical exchange, from a second tonesignaling automatic exchange comprising:a. first and second terminatingsets for connecting four-wire circuits to two-wire circuits, each havinga first and a second pair of wires on the four wire side thereof, b.connecting means for establishing connections between said first andsecond terminating sets, c. said first terminating set receiving on itstwo-wire circuit an input from said tone signaling automatic exchange,d. frequency detecting means receiving tone signals from said first pairof wires of said first terminating set, e. logic means receiving signalsfrom said frequency detecting means, and f. relay means responsive tosaid logic means for closing and opening circuit paths responsive tosaid tone signaling exchange, thereby providing alternative connectionto said electromechanical exchange through extension subscriberequipment or through public network line equipment.
 3. A junctor asrecited in claim 2 further comprising additional relay means responsiveto signals from said first electromechanical exchange.
 4. A junctor asrecited in claim 3 further comprising a modulated signal frequencygenerator connected to said second pair of wires of said firstterminating set responsive to said relay means and to said additionalrelay means.
 5. A junctor as recited in claim 4 wherein said modulatedsignal frequency generator comprises a single-frequency generatormodulated by on-off keying of a keying modulator.
 6. A junctor asrecited in claim 4 wherein said alternative connection is made by saidsecond terminating set on its two wire circuit, responsive to said relaymeans.
 7. A junctor as recited in claim 6 wherein said connecting meanscomprises first and second amplifying means,a. said first amplifyingmeans having an input and an output, said input being connected to saidfirst pair of said first terminating set, and said output beingconnected to said first pair of said second terminating set and to saidfrequency detecting means, and b. said second amplifying means having anoutput connected to said second pair of said first terminating set, andfirst and second inputs,i. said first input connected to said modulatedsignal frequency generator through contacts of said relay means andthrough contacts of said additional relay means, and ii. said secondinput connected to said second pair of said second terminating set.
 8. Ajunctor as recited in claim 7 further comprising off hook detectingmeans responsive to said first exchange for controlling said additionalrelay means.
 9. A junctor as recited in claim 8 wherein said off hookdetecting means comprises first and second off hook detectors,a. saidfirst off hook detector being responsive to an off hook condition duringan emission phase of a ringing signal of said first exchange, and b.said second off hook detector being responsive to an off hook conditionoccurring during a silence interval of the ringing signal.
 10. A junctoras recited in claim 9 wherein said first and second off hook detectorsprovide signals to an OR-type logic element, thereby activating saidadditional relay means when either off hook condition is detected.
 11. Ajunctor as recited in claim 8 wherein said second exchange comprises acomputer controlled, three-frequency signaling system.
 12. A junctor asrecited in claim 11 wherein said second exchange transmits twofrequencies at a time, thereby enhancing reliability.
 13. A junctor asrecited in claim 12 wherein said second exchange comprises atime-division-multiplexed apparatus.
 14. A junctor as recited in claim11 wherein said frequency detecting means comprises first, second andthird frequency detectors.
 15. A junctor as recited in claim 14 whereinsaid logic means comprises first, second and third AND logic elements,whereina. said first logic element receives outputs of said first andsecond frequency detectors, b. said second logic element receivesoutputs of said second and third frequency detectors, c. said thirdlogic element receives outputs of said first and third frequencydetectors, d. said first and second logic elements together control abistable relay having four contacts, and e. said third logic elementcontrols a single contact relay and a two contact relay, responsive toone of said four contacts of said bistable relay.
 16. A junctor asrecited in claim 15 wherein said two-contact relay is activated by afourth AND logic element having first and second inputs,a. said firstinput receiving an output of said third logic element through said oneof said four contacts of said bistable relay, and b. said second inputreceiving an output of a NOT logic element receiving its input from saidoff hook detecting means.
 17. A junctor as recited in claim 16 furthercomprising first and second transformer means for providing saidalternative connection between said second terminating set and saidfirst exchange.